Self-energizing rail clamp

ABSTRACT

A rail clamp for anchoring a traveling crane or vehicle to its runway rail which includes coacting clamp means for simultaneously engaging the upperside and the underside of the railhead. The clamp means engaging the underside of the railhead is in the form of a hook-shaped member, while the clamp means for engaging the upperside is in the form of a plurality of sprags which frictionally engage the railhead upper surface when the clamp is subjected to a force parallel to the runway rail. The clamp develops extremely high forces resistant to movement of the clamp relative the rail by the application of a small force.

[ Apr. 30, 1974 United States Patent [191 Molt [ SELF-ENERGIZING RAIL CLAMP Primary Examiner-(jerald M. Forlenza Assistant Examiner-Richard A. Bcrtsch 75 l t Ri ha d P. M It, Ol F' Ids, lll. l men or c r o ympld le s Attorney, Agent, or FirmLockwood, Dewey, Zlckert [73] Assignee: Whiting Corporation, Harvey, Ill. & Al

[22] Filed:

Aug. 30, 1972 [21] Appl. No.: 284,902

[ ABSTRACT A rail clamp for anchoring a traveling crane or vehicle 188 43, 104/258 to its runway rail whlch includes coactlng clamp means for simultaneously engaging the upperside and B61h 7/12 the unders1de of the rallhead. The clamp means en- 104/2, 7, 8, 258, 188/67,

188/43 41 gaging the underside of the rallhead 1s m the form of a [52] US. [51] Int. [58] Field of Search.......

hook-shaped member, while the clamp means for engaging the upperside is in the form of a plurality of sprags which frictionally engage the railhead upper Zavatkay Syckle.'......

7/1918 Freimark 10/1958 Snow, Jr.

22 Claims, 11 Drawing Figures PATENTEUAPR 30 1974 SHEET t BF 4 FIGJ , l SELF-ENERGIZING RAIL CLAMP This invention relates in general to a rail clamp for anchoring a wheeled rail vehicle to a rail, and more particularly to a rail clamp that is capable of clamping against the upper and lower sides of a railhead to provide an extremely large resisting force with the application of a small force, and still more particularly to a rail clamp for a traveling crane that is capable of anchoring the crane to its runway rail in either direction and operable equally well with railheads of varying depths caused by wear and rolling tolerances.

The present invention of a rail clamp, while useful for any type of traveling crane to anchor the crane to its rail at any selected position, isespecially useful for outdoor cranes. The rail clamp is especially useful to anchor a traveling outdoor crane against high wind forces. For example, a gantry crane which extends vertically a substantial distance presents considerable resistance to high winds which can cause it to roll along the rails and/or toppling of same unless it is anchored against movement. The rail clamp of the invention in clamping position provides resistance to rolling motion in either direction, as well as resistance to overturning motion.

Heretofore rail clamps used with traveling cranes have included jaws that would engage opposite vertical sides ofa railhead forclamping and anchoring ofa traveling crane to its runway rail. Such a rail clamp was unsatisfactory because of the loose tolerances in railhead widths and the necessity to operate such a device within such close tolerances that at times the clamping action would not be effective and therefore the crane would not be firmly clamped to its runway rail.

The rail clamp of the present invention overcomes the heretofore known difficulties in that it is capable of providing a proper clamping of the railhead of a runway rail even where the railhead varies in depth and/or width along any one length of rail. Further, the rail clamp is capable of providing such clamping relationship with a railhead as to apply both horizontal shear forces to resist wind forces and downward forces to resist overturning of the crane. A traveling crane will usually be equipped with wheeled trucks that define a rolling engagement with runway rails to permit the crane to travel along the rails and accomplish desired hoisting and transferring operations. The rail clamp of the invention is mounted on a crane truck, and for any given crane, one ormore clamps may be used on any number of the crane trucks. The rail clamp is suitably carried by a truck between the wheels of the truck andis operable for clamping the runway rail and anchoring the truck to the rail at any selected position, either in locked position or to resist a predetermined force. Where the clamp resists only a set force, an accident that may result from accidental application during rolling can be eliminated.

The rail clamp of the invention generally includes a first clamping means for engaging the underside of the railhead, a second clamping means for engaging the upperside of the railhead. and force applying means causing both clamping means to apply a squeezing force to the railhead. The first clamping means is in the form of one or more hook-shaped members which are carried on a frame mounted for a limited vertical movement in a bracket secured to the crane truck. The second clamping means is suitably connected to the frame by the force applying means, such as in the form of a toggle linkage and therefore movable relative to the frame pursuant to actuation of the toggle linkage. Other forms of force applying means may be used, such as a cam drive unit. A plurality of sprags of hardened tool steel or the like form the second clamping means wherein the sprags are positioned vertically when first contacting the railhead surface. A sprag as used herein refers to an element having a long major dimension and a short minor dimension, wherein it is supported along the major dimensionbetween and in frictional engagement with two opposed relatively movable surfaces, one of which is stationary, such that tilting or cocking of the sprag occurs during relative movement of the surfaces along the minordimension resulting in effectively increasing the length of the sprag to substantially increase the frictional engagement between the sprag and the surfaces and resist further relative movement. In the event of a wind force parallel to the runway rail of sufficient magnitude to move the crane, the sprags are caused to tilt or lean away from the wind force to provide a wedging action and increase substantially the frictional forces applied by the sprags and hook-shaped members to the railhead to match the wind forces and prevent relative movement between the railclamp and the runway rail. Means is provided for mounting the sprags so that a resilience is provided in the toggle linkage to compensate for a variance in railhead depth and still provide the needed initial pressure to develop frictional clamping of the railhead. I

Energization of the rail clamp is accomplished by actuation of the toggle linkage which, when actuated to cause the clamp to assume clamping position, simultaneously causes the engagement of the hook-shaped clamping members to the underside of the railhead and the sprags to the upperside of the railhead, thereby applying squeezing forceto the railhead. Along a given section of the rail which the clamp engages when energized, a relatively small downward force is applied to the upperside of the railhead by the sprag clamping member, while upward forces are applied to the underside of the railhead at points on opposite sides of the sprag clamping member by a pair of hook-shaped clamping members. An actuating arm having a weight thereon extends from the toggle linkage, which when released, gravitationally forces the arm downwardly to extend the toggle linkage into an energizedposition and apply initial clamping pressures to the sprag and hook-shaped clamping members. Any suitable power means may be provided to lift the actuating arm for deenergizing the rail clamp. Likewise, the actuating arm may be powered to straighten the toggle by means other than a weight. For example, a pneumatic or hydraulically operated fluid motor may be used for moving the actuating arm in one or both directions. The displacement or movement of the toggle linkage may be limited to prevent over-center movement and overcenter locking of the toggle linkage and clamping members into locked position to limit the resisting force defined by the clamp. The displacement may be adjusted to limit the maximum force which the clamp can apply, for example, to equal twice the amount of any expected wind force. Inasmuch as the clamp is self-energizing upon the de-en'ergization of a power release means, failure of the power means and energization of the rail clamp when the crane is traveling on the rails will not result in a dead-stop actuation of the rail clamp because of the limited displacement of the toggle linkage. It should be further recognized where a maximum braking force is desired by the clamp, the toggle linkage would be allowed to go over-center whereby the force would then be limited only by the strength of the clamp components.

It is therefore an object of the present invention to provide a new and improved rail clamp for traveling cranes.

A further object of this invention is in the provision of a rail clamp for use on trucks of traveling cranes wherein the clamp may be self-energizing.

A still further object of this invention is to provide a rail clamp for anchoring a traveling crane to its runway rail at any selected position to counter forces that would tend to drive the crane from the rails and thereby cause substantial crane damage.

A further object of this invention is in the provision of a rail clamp for anchoring trucks of a traveling crane to its runway rails which clamps against the upper and lower sides of the railhead to apply squeezing forces thereto and which is capable of providing proper clamping action even where a variance in railhead width or depth is encountered along a runway rail.

A further object of this invention is to provide a rail clamp for anchoring a traveling crane to its runway rail capable of applying to the railhead both horizontal shear forces to resist wind forces and downward forces to resist overturning.

A still further object of this invention is in the provision of a rail clamp for anchoring a traveling crane to its runway rails wherein the rail clamp includes means for applying clamping forces to theupper and lower sides of the runway railhead and for'compensating for a variation in railhead depth while still providing a satisfactory clamping action.

Another object of the invention is to provide a rail clamp for wheeled trucks moving along rails wherein the clamp is capable of developing a clamping action that will resist any applied wind or inertia force limited only by the design strength of the clamp, or may be adjusted to develop a clamping action that will resist only a predetermined force.

Other objects, features and advantages of the invention will be apparent from the following detailed disclosure, taken in conjunction with the accompanying sheets of-drawings, wherein like reference numerals refer to like parts, in which. 2

FIG. 1 is a perspective view ofa traveling crane of the type that would utilize the rail clamp of the invention in the crane trucks;

FIG. 2 is a fragmentary view of a crane truck with parts broken away and showing the rail clamp of the invention mounted on the truck and in association with the railhead of the runway rail and illustrating the clamp energized with the parts shown in solid lines and the clamp de-energized with the parts shown in phantom;

FIG. 3' is a fragmentary enlarged view of therail clamp of the invention shown in side elevation with some parts broken away to show underlying parts in section and illustrating the clamp in energized position and taken generally along line 3-3 of FIG.

FIG. 4 is a fragmentary ,view of a portion of the rail clamp of the invention illustrating the manner in which the sprags tilt or cock and effectively lengthen when a wind force is applied to the clamp through the crane and crane truck;

FIG. 5 is a vertical sectional view taken through the rail clamp substantially along line 5-5 of FIG. 3 and showing the clamp in energized position;

FIG. 6 is a vertical sectional view taken through the clamp and generally along line 6-6 of FIG. 3;

FIG. 7 is a side elevational view of the rail clamp according to the invention and illustrating somewhat diagrammatically the actuation of the clamp where the toggle is in over-center locking position;

FIG. 8 is a side elevational view ofa sprag used in the rail clamp of the invention;

FIG. 9 is an end elevational view of the sprag;

FIG. 10 is a side elevational view of a modification where a cam drive is used in place of the toggle linkage for driving the rail clamp into clamping position; and

FIG. 11 is an end elevational view of a modification where the jaws for engaging the underside of the railhead are movable outwardly so as to enable the complete lifting of the rail clamp and the removal of the vehicles or trucks associated with the rail clamp from the rail.

Referring now to the drawings and particularly to FIG. 1, a traveling crane 10 in the form of a gantry crane is shown, which includes a plurality of trucks 11 having wheels 12 in rolling engagement with runway rails 13 wherein the crane may travel along the rails when performing work functions. The rail clamp of the invention is adapted to be associated with a truck of a crane and may be mounted on any one or all of the trucks. It should be appreciated that the crane l0 illustrates only one form, of traveling crane having trucks with which therail clamp of the invention may be used and that the rail clamp may be utilized on trucks of any type crane or other rail supported vehicle.

The rail clamp of the invention, generally designated by the numeral 15, is illustrated in FIG. 2 in mounting relationship on a crane truck wherein it is arranged at the rail between the wheels 12 of the truck and between opposing truck side plates I6, 16. Spaced mounting beams 17, 17 extend between the opposing truck side plates 16, 16 and are secured thereto for the purpose of mounting therebetween the rail clamp 15. Any other suitable support for the rail clamp may be provided.

The crane runway rail 13, which is of standard configuration, includes a tie flange 20 adapted to be mounted on and secured to a suitable support or ties, an upstanding web 21 extending upwardly from the tie flange, and a wheel-head 22adapted to receive the wheels 12 of the trucks and to be clamped by the rail clamp 15 when it is energized to anchor the crane truck or trucks to the rail The railhead includes an upper side or surface 23 extending generally horizontally and upon which the truck wheels 12 roll, opposed substantially vertically extending side surfaces 24, 24 and a pair of under or bottom surfaces 25, 25, hereinafter referred to generally as the underside of the head or the undersurface of the head. The undersurfaces 25 are at the opposite sides of the web 21. The rail clamp of the invention, when in clamping relation with 'the runway railhead, frictionally engages both the upper and lower surfaces 23 and 25 of the railhead to apply thereto both horizontal shear forces to resist wind forces parallel to the runway rails and downward forces to resist overturning of the crane. The clamp effectively applies squeezing forces to the railhead.

The rail clamp of the invention includes generally a pair of parallel opposed support brackets 28, 28 (FIG. 3) that are carried by the mounting beams 17 and which extend perpendicular to the runway rail, an inverted U-shaped frame 29 arranged between the support brackets 28 and mounted thereon for limited vertical movement relative thereto and having a pair of hook-shaped clamping members 30, 30 that extend downwardly over the railhead and are adapted for clamping engagement with the underside of the railhead, a sprag clamp member or cage 31 positioned between the hook-shaped clamping members 30 and di rectly over the top of the railhead and having a plurality of clamping members in the form of sprags 32 of hardened tool steel for engaging the upper side of the railhead when the clamp is energized, a mechanism for causing the clamping members 30 and 32 to develop a squeezing force between them in the form of a toggle mechanism or linkage 33 connecting the sprag cage to the frame 29 and providing the clamping pressure or applying force for the sprag cage 31 and the hookshaped members 30 when the rail clamp is energized, an actuating arm 34 having a weight 35 thereon for actuating the toggle linkage 33 and a fluid cylinder 36 for controlling the energization of the rail clamp. Other types of mechanisms may be used in place of the toggle mechanism to create a high mechanical advantage and actuate the clamping members, which during energization of the clamp will develop frictional forces within the mechanism that opposes the engagement of the clamping members and serves to limit the ratio relationship between the engagement force and the clamping normal force applied to the sprag cage. When the clamp is to be de-energized, these same frictional forces change direction and tend to oppose disengagement. The effects of these frictional forces are predictable within certain limits, and they can be controlled by design to provide, for a given actuation force, any desired level of effective mechanical advantage and associated resisting shear force from a very low to a very high value approaching infinity.

An example of another mechanism capable of actuating the clamping members and developing the necessary frictional forces is illustrated in FIG. 10, where instead of a toggle mechanism, a cam or eccentric drive mechanism is used. With respect to like parts, the same numerals have been applied. This mechanism includes a cam or eccentric 37 which is solidly connected to the actuating arm 34 and therefore pivotal on the frame 29 and which engages a drive plate 37a connected to the sprag cage 31. Springs 37b are interconnected between the frame 29 and the drive plate 37a to normally urge the drive plate and sprag cage upwardly to disengage the sprags from the railhead when the clamp is deenergized. Actuation of the mechanism is accomplished in the same manner as with respect to the toggle mechanism wherein counterclockwise movement of the actuating arm 34 imparts a similar counterclockwise movement to the eccentric or cam 37 to drive the plate 37a and the sprag'cage 31 downwardly until the sprags engage the railhead. As with respect to the toggle mechanism, an adjustable stop is provided to limit the movement of the cam 37 so that the cam can be allowed to move to a resting position before or after dead-center to limit the maximum-resisting forces of the clamp or to allow the resisting forces to reach a maximum. As shown in FIG. 10, the cam is stopped ahead of dead-center.

Accordingly, energization of the rail clamp is accomplished by de-energizing the fluid cylinder 35 and allowing the weighted actuating arm 34 to gravitationally drop and actuate the toggle linkage 33 to cause the clamping members 30 and 31 to respectively frictionally engage the lower and upper sides of the railhead 22 with sufficient pressure that relative movement between the clamp and rail will cause tilting of the sprags to greatly increase the frictional forces between th clamp and railhead.

The frame 29 includes a pair of parallel spaced and vertically extending plates 38, 38 interconnected at their upper ends by means of a cross bar 39. A pair of axially aligned trunnions 40, 40 extend from the outer end surfaces of the vertical plates 38 and are received in vertical slots 41, 41 formed in the support brackets 28. The vertical slots permit limited vertical movement of the frame 29 relative to the support brackets 28 which are stationarily mounted on the truck.

The hook-shaped clamping members 30 are defined by forming the lower end of the vertically extending plates 38 to have a portion 44 (FIG. 6) that extends along one side of the railhead and a terminal portion 45 that extends beneath the railhead at one side of the web and includes an upwardly facing clamping surface 46 for engagement with an under-surface 25 of the railhead when the clamp is energized and a bifurcated member 48 mounted on the plates 38 but removable therefrom for purposes of permitting installation of the rail clamp. i

The bifurcated member 48 includes a pair of opposed plates 49, 49, one adapted to be positioned on each of the opposite sides of the vertical plates 38 of the frame 29 and which are interconnected by a pair of cross bars 50, 51. The upperends of the plates 49 include open circular sockets 52 for engaging and hanging on a pin 53 that is carried in the vertical plate 38 and extends from each side thereof. A downwardly extending portion 54 extends along one side of the railhead and terminates below the railhead in a terminal portion 55 having an upwardly facing clamping surface 56 engageable with the other undersurface 25 of the railhead. A bolt 57 is threadedly anchored in the vertical plate 38 and having its head extending into a socket formed in one of the plates 49 (FIG. 3) for the purpose of locking the bifurcated member 48 in place on the vertical plate 38. The clamping members 30 and the lower ends of the vertical plate 38 are held in proper spaced relation by means of a longitudinally extending angle bar 58 which extends between the vertical plates 38 and is suitably attached thereto, such as by welding or the like.

During the traveling of the crane truck along the runway rail when the rail clamp is de-energized, the clamping faces or surfaces 46 and 56 of the clamping members 30 clear the underside or undersurfaces of the railhead, such as shown in phantom in FIG. 6. In order to prevent frictional engagement of the clamping members 30 with the opposed vertical surfaces 24 of the railhead, followers or rollers 59 and 60 are mounted on the lower ends of the clamping members 30 at opposite sides for engagement with the opposed vertical surfaces of the railhead.

The sprag clamping member or cage 31 situated between the hook-shaped clamping members 30 includes upper parallel spaced support lugs 63, 63 carrying a pin 64 for pivotal connection to the toggle linkage 33. A horizontally extending upper plate 65 is suitably secured to the lugs 63. Vertically and downwardly extending opposed sprag support plates 66, 66 are arranged at opposite ends of the upper plate 65 and extend substantially parallel to the frame plates 38 and clamping members 30. A sprag mounting rod 67 is supported by and extends between the sprag support plates 66 adjacent their lower ends.

Central openings 69 are formed in the sprags for aligning and mounting on the rod 67. Wedge-shaped blocks 68, 68 are mounted at the inner sides of each of the sprag support plates 66 and at the opposite ends of the sprags 32 and provide inclined surfaces 680 and 68b which respectively assist tilting or cocking the sprags 32 in one direction, such as illustrated in FIG. 4 per surface 68a, or in the other direction in response to a wind or other inertia force on the rail clamp along the rail. It should be appreciated structures equivalent to the wedge-shaped blocks may be used, such as pins; and further that no tilt assist means is essential to ob tain tilting, because friction alone assures tilting will occur when the railhead and sprag plate move relative each other. As seen particularly in FIGS. 3 and 9, the central openings 69 of the sprags are flared at opposite ends at 69a and 69b to permit tilting of the sprags on the supportrod 67.

The sprags are generally rectangular in shape, viewed from the side as in FIGS. and 8, to provide an upper face or end 70 and a lower rail engaging face or end 72, the latter being in engagement with the upper side 23 of the railhead when the clamp is energized. As seen in FIG. 5, the lower face 72 extends across the railhead uppersurface and perpendicular to the rail. When the sprags tilt on the mounting rod, either the edge 73 or the edge 74 of the rail engaging face 72will frictionally engage the upperside of the railhead. The edge 73 is in frictionally engaging relation with the railhead uppersurface in the illustration of FIG. 4.

In order to compensate for a variation in railhead depth which may be caused due to wear and to rolling tolerances, an elastomeric cushion member 75 is interposed between the upper plate 65 and a movable sprag plate or'platen 77 whichengages the upper ends of the sprags 32. It should be appreciated the cushion 75 delines a biasing force between the plates 65 and 77, and that one or more springs could be used in place of the cushion. The sprag plate 77 is carried on the upper plate 65 and movable relative thereto by means of a pair of bolts 78,'78 which extend through bores 79 formed in the upper plate 65 and are threadedly anchored in the movable sprag plate 77. The heads of the bolt 78 limit the downward movement of the movable sprag plate 77, while the cross-sectional shape of the plate 77, as shown in FIG. 5, provides a cavity 80 in the form of a slot for receiving theelastomeric member 75 wherein opposed upper bearing surfaces 81 limit the deformation of an elastomeric member 75 and movement of the plate 77 when they bottom on the underside of the upper plate 65. The resilience of the elastomeric cushion 75 assures that the toggle linkage 33 can assume a high force, nearly straight configuration, even though variations in railhead depth are encountered along the length of the rail.

Moreover, the lower end or face 72 is chamfered or relieved at each side as indicated at 73a and 74a to assist in initial tilting on a slippery railhead.

The toggle linkage 33 includes a lower link 85 pivotally carried at its lower end on the pin 64 of the sprag clamping member 31 and pivotally connected to an upper link 86 by means of a pin 87 at the toggle joint. The upper link 86 is in the form of a pair of spaced bars that are arranged on opposite sides of the cross bar 39 of frame 29 and pivotally connected to a pin 88 extending through the cross bar. The upper link 86 is solidly connected to the actuator arm 34 which is in the form of a pair of spaced bars and which extend substantially at right angles to the link 86 and laterally of the rail clamp.

The outer free end of the actuator arm 34 is pivotally connected to the piston rod 91 of the fluid cylinder 35, which is in turn pivotally connected at 92 to a bracket 93 carried on the truck 11.

The displacement of the toggle linkage 33 is limited by an adjusting bolt 96 mounted in one of the vertical plates 38 of the frame 29 and extending inwardly in alignment with the toggle joint of the toggle linkage. The adjusting bolt is usually adjusted to prevent the toggle joint from moving into or over dead-center, thereby limiting the maximum force whichthe clamp can apply to the rail, such, forexample, to twice as large as any maximum expected wind force. In the event the clamp is desired to apply a maximum braking force, the toggle mechanism may be allowed to move past dead-center into overcenter locking position by adjustment of the bolt 96 as shown in FIG. 7, wherein the resisting forces developed by the clamp are only limited by the design strength. Within this adjustment, the sprags 32 are self-energizing and will move in direction and quantity to oppose any applied force which the truck imposes on the rail clamp through the brackets 28.

In operation, when the clamp is to be energized, the fluid cylinder 35 is de-energized to allow the weighted actuating arm 34 to lower and actuate the toggle linkage 33 until the toggle joint bears against the stop of the adjusting bolt 96 and which will cause downward movement-of the sprag clamping member 33 until the sprags 32 engage the uppersurface of the railhead 22 and upward movement of the frame 29 and the hookshaped clamping members 30 to cause the clamping faces of the clamping members 30 to engage the undersurfaces of the railhead. This will also cause the trunnions 40 to move to the upper end of the slot 41. The weight on the actuating arm is continually applied while the clamp is energized. Likewise, when the rail clamp 40 is de-energized, the trunnions 40 will be at the lower end of the slot 41. With the rail clamp thusly energized,a wind force parallel to the runway rails will attempt to move the crane, either from the left or right as viewed in FIG. 4, and cause the'sprags 32 to tilt and lean away from the wind force. While the frictional engagement at the top and bottom of the sprags will cause tilting, the members 68 will assist in tilting. When the sprags roll, such as illustrated in FIG. 4, they increase the distance between the railhead and the bearing plate 77 causing squeezing of th'elastomeric cushion until the bearing plate bottoms against the upper plate 65 or sprag housing and at which time the sprag force on the rail increases dramatically, increasing the existing frictional forces on both the sprags and at the rail clamp surface to match the applied wind force. The release force necessary to open the clamp exceeds the setting force. Thereafter, de-energization of the rail clamp is accomplished by energizing fluid cylinder 35 to lift the actuator arm 34 and release the force of the toggle linkage 33 to raise the sprag housing from the top of the rail and lower the hook-shaped clamping members from the underside of the railhead.

In the event the rail clamp is in de-energized position and the crane is traveling along the rails at some finite speed, should the fluid cylinder 35 fail and allow the toggle linkage actuating arm to lower and actuate the toggle linkage to less an overcenter position, the forces encountered by the clamping members attempting to frictionally engage the rail clamp will counter the force of the weighted actuating arm and prevent full clamping action and a sudden stop. Such would avoid damage to the crane, for if full clamping action were encountered while the crane is moving, the sheer weight of the crane might cause damage to the crane such as toppling same.

While the rail clamp of the invention will be primarily useful in connection with the anchoring or braking of outdoor traveling cranes on rails, it should be appreciated that it could be used with other wheeled vehicles on rails. For example, it could be used on any type of rail car for the purpose of anchoring the car at any selected position on the rails, but in this case it would not be normally possible to allow the hook-shaped clamping members of the rail clamp to remain in a position about the rail such as illustrated in FIGS. 2 to 6, for there would be obstructions that would interfere with the movement of the hook-shaped clamping members along the rails. Therefore, it should be appreciated that suitable mechanism may be provided for retracting the rail clamp from the rail after it has been de-en'ergized and in which case it will be further necessary to open the jaws of the hook-shaped clamping members to allow retracting of the rail clamp. FIG. 11 merely illustrates diagrammatically such an arrangement where the hook-shaped clamping members can be manipulated to enable raising of the rail clamp. More specifically, a set of hook-shaped clamping members 100 would include clamping jaws 101 and 102 selectively movable about a pivot pin 103 by the application of suitable forces to drive arms 104 and 105. It can be appreciated that any suitable mechanism can be employed for operation of the drive arms to drive the jaws 101 and '102 into engaging position about the railhead of the rail, as shown in solid lines, or to disengaging position, as shown in phantom, where the clamp may be raised about the rail.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention, but it is understood that this application is to be limited only by the scope of the appended claims.

The invention is hereby claimed as follows:

1. In combination with a truck for a wheeled rail vehicle movable alonga runway rail, wherein the rail includes a tie flange, a web upstanding from the flange, and a railhead on top of the web, a rail clamp coacting with the railhead for clamping the truck to the rail comprising, a frame having first clamp means engagable with the underside of the railhead and second clamp means movable relative said first clamp means and engagable with the upperside of the railhead, one of said clamp means including a plurality of tiltable mounted sprags, means mounting the frame for limited vertical movement such that when the clamp is de-energized said first clamp means clears the underside of the railhead and said second clamp means clears the upperside of the railhead, means mounting said first clamp means to said frame to move therewith, high mechanical advantage means mounting said second clamp means on said frame such that both clamp means are movable to engage the railhead upon actuation thereof and apply a squeezing force thereto when the mechanical advantage means is actuated wherein the sprags produce a locking wedging action with the railhead, and means for actuating said high mechanical advantage means.

2. The rail clamp of claim 1, wherein said first clamp means includes means engaging the underside of said railhead at opposite sides of the Web.

3. The rail clamp of claim 1', wherein said first clamp means includes at least one pair of hook-shaped coacting jaws having a pair of rail engaging faces for engaging the underside of the railhead.

4. The rail clamp of claim 1, wherein said first clamp means includes two pairs of hook-shaped coacting jaws, each having a pair of rail engaging faces for engaging the underside of the railhead, one pair of jaws being positioned on each sideof said second clamp means.

5. The rail clamp of claim 1, wherein said second clamp means includes a housing and the plurality of sprags carried thereby and engagable with the railhead when the clamp is energized.

6. The rail clamp of claim 5, wherein said housing includes means mounting said sprags to cause tilting in a direction away from a force being applied to the clamp to increase the frictional engagement between the clamping members and the railhead.

7. The rail clamp of claim 6, wherein said housing includes means associated with the sprags to provide proper clamping action while compensating for a variance in railhead depth.

8. The rail clamp of claim 7, wherein said compensating means includes a movable sprag bearing plate carried on the housing and engaging the upper ends of the sprags, and'elastomeric means interposed between the bearing plate and the housing.

9. The rail clamp of claim 1, andmeans mounting the frame to a bracket support means, wherein said means mounting the frame to the bracket support means includes trunnion means on said frame received in vertical slot means formed in said bracket support means.

10. The rail clamp of claim 1, and stop means controlling the displacement of said high mechanical advantage means. 7

11. The rail clamp of claim 10, wherein the stop means is adjustable to control the maximum clamping 13. The rail clamp of claim 1, wherein said high mechanical advantage means is a toggle linkage mechanism.

14. The rail clamp of claim 1, wherein said high mechanical advantage means is a cam drive mechanism.

15. In combination with a truck for a traveling crane movable along a runway rail, wherein the rail includes a tie flange, a web upstanding from the flange, and a railhead on top of the web, a rail clamp for locking the truck to the rail by clamping frictionally to the top and bottom surfaces of the railhead comprising a'clamp head, at least one pair of coacting jaws extending from the head and engagable with the underside of the railhead, a self-energizing sprag head on the clamp head movable toward and away from the topside of the railhead and causing the jaws to synchronously move toward and away from the underside of the railhead to apply a squeezing force thereto when the sprag head is energized wherein the sprag head produces a locking wedging action with the railhead, said sprag head including a plurality of tiltable mounted sprags, and means for de-energizing the clamp.

' 16. A rail clamp mountable on a truck of a traveling crane movable along a runway rail to anchor the crane at any selected position to counter wind forces, wherein the rail includes a head having an upper wheel engaging surface and opposed undersurfaces, said rail clamp including a pair of hook-shaped clamping members for extending around the railhead and engaging the under-surfaces thereof at. spaced points along the railhead and a sprag clamping member for engaging the upper rail surface at a point intermediate the points of engagement by the hook-shaped members, a pair of spaced bracket supports carried by the crane truck, an inverted U-shaped frame between the brackets including an upper cross bar and downwardly extending legs, means mounting the frame to the brackets for limited vertical movement therewith, said hook-shaped clamping members being carried on the legs of said frame and said sprag clamping member being arranged between the legs, a toggle linkage means between the frame and sprag clamping member, an actuating arm extending laterally from the toggle linkage means, a weight on said actuating arm to actuate said toggle linkage means and energize the clamp, and means connected to the actuating arm for de-energizing same.

17. The rail clamp of claim 16, wherein means is pro- 7 vided to limit the displacement of the toggle linkage to thereby limit the maximum force applied by the clamp.

18. The rail clamp of claim 17, wherein said displace ment limiting means is adjustable.

19. The rail clamp of claim 17, wherein means is provided between the sprag clamping member and the toggle linkage means to define a resilience such that the toggle linkage means can assume a high force, nearly straight configuration, even though variations in railhead depth are encountered along the length of the rail.

20. The rail clamp of claim 19, wherein said sprag clamping member includes a plurality of upstanding side-by-side disc-like hardened sprags aligned with the railhead and extending transverse thereto, and means for tilting the sprags in the event a force is applied to the clamp to increase the frictional engagement with the railhead.

21. The rail clamp of claim 17, wherein said sprag clamping member includes an inverted U-shaped housing having an upper cross plate and downwardly extending side plates, a plurality of upstanding, rectangular in cross section,'side-by-side, disc-like hardened sprags aligned with the railhead and extending transverse thereto arranged between the side plates, a bearing plate positioned between the side plates and below the cross plate for engagement with the upper ends of the sprags and mounted to the cross plate for limited vertical movement therewith, means between the cross plate and bearing plate exerting a force to bias said plates apart, and means at the side plates engaging said sprags when the clamp is energized and a force is applied to the clamp along the rail to tilt the sprags in a direction away from the force, thereby increasing the distance between the railhead and the bearing plate to ultimately bottom the bearing plate on the cross plate and increase the frictional resisting forces applied by the clamp.

22. The rail clamp of claim 16, wherein said hookshaped clamping members include coacting jaws one on each side of the rail, and means for selectively moving the jaws into rail engaging position during energization of the clamp and out of rail engaging position to allow removal of the clamp from the rail. 

1. In combination with a truck for a wheeled rail vehicle movable along a runway rail, wherein the rail includes a tie flange, a web upstanding from the flange, and a railhead on top of the web, a rail clamp coacting with the railhead for clamping the truck to the rail comprising, a frame having first clamp means engagable with the underside of the railhead and second clamp means movable relative said first clamp means and engagable with the upperside of the railhead, one of said clamp means including a plurality of tiltable mounted sprags, means mounting the frame for limited vertical movement such that when the clamp is de-energized said first clamp means clears the underside of the railhead and said second clamp means clears the upperside of the railhead, means mounting said first clamp means to said frame to move therewith, high mechanical advantage means mounting said second clamp means on said frame such that both clamp means are movable to engage the railhead upon actuation thereof and apply a squeezing force thereto when the mechanical advantage means is actuated wherein the sprags produce a locking wedging action with the railhead, and means for actuating said high mechanical advantage means.
 2. The rail clamp of claim 1, wherein said first clamp means includes means engaging the underside of said railhead at opposite sides of the web.
 3. The rail clamp of claim 1, wherein said first clamp means includes at least one pair of hook-shaped coacting jaws having a pair of rail engaging faces for engaging the underside of the railhead.
 4. The rail clamp of claim 1, wherein said first clamp means includes two pairs of hook-shaped coacting jaws, each having a pair of rail engaging faces for engaging the underside of the railhead, one pair of jaws being positioned on each side of said second clamp means.
 5. The rail clamp of claim 1, wherein said second clamp means includes a housing and the plurality of sprags carried thereby and engagable with the railhead when the clamp is energized.
 6. The rail clamp of claim 5, wherein said housing includes means mounting said sprags to cause tilting in a direction away from a force being applied to the clamp to increase the frictional engagement between the clamping members and the railhead.
 7. The rail clamp of claim 6, wherein said housing includes means associated with the sprags to provide proper clamping action while compensating for a variance in railhead depth.
 8. The rail clamp of claim 7, wherein said compensating means includes a movable sprag bearing plate carried on the housing and engaging the upper ends of the sprags, and elastomeric means interposed between the bearing plate and the housing.
 9. The rail clamp of claim 1, and means mounting the frame to a bracket support means, wherein said means mounting the frame to the bracket support means includes trunnion means on said frame received in vertical slot means formed in said bracket support means.
 10. The rail clamp of claim 1, and stop means controlling the displacement of said high mechanical advantage means.
 11. The rail clamp of claim 10, wherein the stop means is adjustable to control the maximum clamping force of the clamp.
 12. The rail clamp of claim 11, wherein the means for actuating the high mechanical advantage means includes a weighted self-energizing actuating arm, and power means for lifting the arm to de-energize the clamp.
 13. The rail clamp of claim 1, wherein said high mechanical advantage means is a toggle linkage mechanism.
 14. The rail clamp of claim 1, wherein said high mechanical advantage means is a cam drive mechanism.
 15. In combination with a truck for a traveling crane movable along a runway rail, wherein the rail includes a tie flange, a web upstanding from the flange, and a railhead on top of the web, a rail clamp for locking the truck to the rail by clamping frictionally to the top and bottom surfaces of the railhead comprising a clamp head, at least one pair of coacting jaws extending From the head and engagable with the underside of the railhead, a self-energizing sprag head on the clamp head movable toward and away from the topside of the railhead and causing the jaws to synchronously move toward and away from the underside of the railhead to apply a squeezing force thereto when the sprag head is energized wherein the sprag head produces a locking wedging action with the railhead, said sprag head including a plurality of tiltable mounted sprags, and means for de-energizing the clamp.
 16. A rail clamp mountable on a truck of a traveling crane movable along a runway rail to anchor the crane at any selected position to counter wind forces, wherein the rail includes a head having an upper wheel engaging surface and opposed undersurfaces, said rail clamp including a pair of hook-shaped clamping members for extending around the railhead and engaging the under-surfaces thereof at spaced points along the railhead and a sprag clamping member for engaging the upper rail surface at a point intermediate the points of engagement by the hook-shaped members, a pair of spaced bracket supports carried by the crane truck, an inverted U-shaped frame between the brackets including an upper cross bar and downwardly extending legs, means mounting the frame to the brackets for limited vertical movement therewith, said hook-shaped clamping members being carried on the legs of said frame and said sprag clamping member being arranged between the legs, a toggle linkage means between the frame and sprag clamping member, an actuating arm extending laterally from the toggle linkage means, a weight on said actuating arm to actuate said toggle linkage means and energize the clamp, and means connected to the actuating arm for de-energizing same.
 17. The rail clamp of claim 16, wherein means is provided to limit the displacement of the toggle linkage to thereby limit the maximum force applied by the clamp.
 18. The rail clamp of claim 17, wherein said displacement limiting means is adjustable.
 19. The rail clamp of claim 17, wherein means is provided between the sprag clamping member and the toggle linkage means to define a resilience such that the toggle linkage means can assume a high force, nearly straight configuration, even though variations in railhead depth are encountered along the length of the rail.
 20. The rail clamp of claim 19, wherein said sprag clamping member includes a plurality of upstanding side-by-side disc-like hardened sprags aligned with the railhead and extending transverse thereto, and means for tilting the sprags in the event a force is applied to the clamp to increase the frictional engagement with the railhead.
 21. The rail clamp of claim 17, wherein said sprag clamping member includes an inverted U-shaped housing having an upper cross plate and downwardly extending side plates, a plurality of upstanding, rectangular in cross section, side-by-side, disc-like hardened sprags aligned with the railhead and extending transverse thereto arranged between the side plates, a bearing plate positioned between the side plates and below the cross plate for engagement with the upper ends of the sprags and mounted to the cross plate for limited vertical movement therewith, means between the cross plate and bearing plate exerting a force to bias said plates apart, and means at the side plates engaging said sprags when the clamp is energized and a force is applied to the clamp along the rail to tilt the sprags in a direction away from the force, thereby increasing the distance between the railhead and the bearing plate to ultimately bottom the bearing plate on the cross plate and increase the frictional resisting forces applied by the clamp.
 22. The rail clamp of claim 16, wherein said hook-shaped clamping members include coacting jaws one on each side of the rail, and means for selectively moving the jaws into rail engaging position during energization of the clamp and out of rail engaging position to allow removal of the clamp from the rail. 